The long range inspection of pipework

One problem with conventional NDT techniques such as standard ultrasonic testing is that they only interrogate the part of the test structure directly beneath the transducer. This means that if a large structure is to be inspected, test times become extremely long and the inspection can add very significantly to operating costs. One way to overcome this problem is to use Lamb waves which propagate along a structure and therefore enable the line between two transducers placed a significant distance apart (up to several metres in pipes) to be inspected in a single test, so resulting in large savings in inspection time. A system developed in the group for the detection of corrosion under insulation in chemical plant pipework is now being marketed by Guided Ultrasonics Ltd, a company set up by ex members of the group. Further details can be found at Guided Ultrasonics Ltd. The current system is designed for use on above-ground exposed or insulated pipes and short buried sections such as road crossings; only very limited pipe lengths can be inspected when the pipe is heavily coated in a very attenuative material such as bitumen or if it is encased in, for example, concrete. This is due to leakage of energy from the pipe into the surrounding medium. Current work in the group is looking at ways to overcome these problems.